Thermostat



Oct. 27, 1970 H. F. SNIDER 3,537,052

' THERMOSTAT Filed Feb. 13, 1969 2 Sheets-Sheet 1 United States Patent Ohio Filed Feb. 13, 1969, Ser. No. 798,944 Int. Cl. H01h 37/04, 37/54 US. Cl. 337-354 12 Claims ABSTRACT OF THE DISCLOSURE A snap disc operated thermostat wherein the body assembly consists of a main body member and a cover member which cooperate to totally enclose the switch elernents and the terminal elements. In addition they provide support for the lead wires. The switch includes two terminal and contact assemblies or units each of which is secured in the body by a single rivet. A unitary disc retainer functions to mount the disc, to secure the body as sembly together, and to cover the access openings for the rivets. The structure is arranged so that its width is substantially equal to the diameter of the snap disc and its thickness is smaller than its width.

BACKGROUND .OF INVENTION This invention relates generally to thermostats and more particularly to a novel and improved small thermostat structure wvhich provides reliable operation and which may be manufactured at a relatively low cost.

PRIOR ART Various types of snap disc operated thermostats are well known. Examples of such thermostates are illustrated in the US. Letters Patents 3,081,388, 3,219,783, and 3,322,- 920. In such devices a bimetallic snap disc operates to open and close a switch. Such thermostats are often used in various types of appliances to control the operation of the appliance.

SUMMARY OF INVENTION The present invention is directed to a novel and improved thermostat structure in which a relatively small number of parts are employed in the manufacture of the thermostat and wherein relatively low manufacturing costs can be obtained without sacrificing reliability and accuracy of operation.

In the illustrated embodiment of this invention a thermostat includes an elongated body assembly consisting of a main body rnember and a cover member. The body assembly is arranged to provide total enclosure of the terminals and to provide support for the lead wires spaced from the terminal connection. The terminals are part of a unitary terminal and contact assembly each of which is secured in the body by a single rivet fastener.

A disc retainer is provided which serves several functions. The retainer secures the disc in position, secures the cover in position against the main body and provides a closure to cover the rivets and thus prevent any external exposure of electrically charged elements.

The thermostat may be used in a variety of installations. As an example, it is illustrated installed in an electrical baseboard heater as a high-limit control. In this installation a plurality of thermostats are connected in series and are mounted at spaced locations along the heater. The provision of a plurality of thermostats at spaced locations along the heater minimizes the danger of excessive heat at a particular location from being undetected. Since the thermostats are connected in series, operation of any of the thermostats serves to terminate current flows 3,537,052 Patented Oct. 27, 1970 ice to the heating elements of the appliance and thereby prevents damaging excessive temperatures from occurring.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a typical electrical baseboard heater illustrating the heater with three thermostats incorporating this invention and connected in series and mounted at spaced locations along the heater;

FIG. 2 is an enlarged perspective view of a single thermostat incorporating this invention;

FIG. 3 is a plan view with the cover element removed illustrating the structural arrangement of the thermostat switch mechanism;

FIG. 4 is a side elevation in longitudinal section;

FIG. 5 is a cross section taken along 5-5 of FIG. 4; and,

FIG. 6 is a cross section taken along 66 of FIG. 4.

A typical electrical baseboard heating appliance 10 is illustrated in FIG. 1. The air to be heated enters the appliance adjacent to the bottom at 11 and the heated air passes out of the appliance through the openings 12. In the illustrated appliance there are three similar thermo stats 13 mounted on the underside of the top of the heater at spaced locations along the heater. These thermostats 13 are connected in series and are connected in the power supply circuit of the heater so that when any one of the thermostats opens the supply of electrical energy to the heater is cut off. These thermostats are considered to be high-limit controls and are arranged so that the switches in the thermostat open when a predetermined temperature is exceeded.

Referring to FIG. 2, each of the thermostats 13 is provided with a body assembly 14 consisting of a main body member 16 and a cover member 17. The members 16 and 17 are preferably molded from a plastic which is resistant to relatively high temperatures and which is electrically insulating in character. The body assembly is secured together by a disc retainer 18 which is formed of sheet metal and is provided with tabs 19 which are bent over into associated recesses 21 in the cover 17. The disc for operating the thermostat is located adjacent to the lower side of the thermostat as viewed in FIGS. 2 through 6.

In the installation of FIG. 1 the thermostat 13 may be mounted against the undersurface on the top of the heater 10 by means of a mounting clamp 170. In the installed position the thermostat is inverted from the position of FIG. 2 and the disc is positioned against the undersurface of the cover. In the illustrated embodiment the cover 17 is provided with projections 17a which extend from opposite sides of the cover through mating openings 17!) in the clip 17c. Further the clip is preferably provided with lateral cut-outs 17d which press against the surface of the cover 17 and prevent looseness. It should be understood that lead wires 27 and 28 extend into opposite ends of the thermostat and are connected internally, as described in detail below, to the terminal of the thermostat. With this arrangement the body assembly 14 provides support for the lead wires at a position spaced from the terminals so the likelihood of wire breakage at the terminal is virtually eliminated.

Referring to FIGS. 3 through 6, the main body member 16 and cover member 17 are molded to cooperate and provide a switch chamber 20 in which the switch elements are located. Mounted within the switch chamber 20 are first and second terminal assemblies or units 22 and 23. The terminal assembly 22 includes a terminal member 24 which is clinched at 26 onto the end of the lead wire 27 to provide an electrical connection therewith. One end of the terminal member 24 is provided with an insulating gripping portion 25 which grips the insulating of the lead wire 27 adjacent to its end. The other end of the terminal member 24 is a flat mounting section 30 positioned to overlie one end of a mobile contact support member 28. The mobile support member 28 is formed of spring material and is provided with stiffening ribs 29 intermediate its end. A mobile contact 31 is mounted on the free end of the contact support 28.

The mobile contact support member 28 may be welded to the terminal member 24 at 32. When a weld connection is provided, it is preferable to form the body member 16 with a relief at 33 to insure that any projection formed during the Welding does not cause the terminal assembly 22 to be incorrectly positioned. If desired, however, the mobile contact support member 28 and the terminal member 22 do not have to be permanently connected so long as a sufficiently good electrical connection is provided along the interface therebetween, for example by silverplating.

A single rivet 34 extends through the assembly 22 and through an opening 36 formed in the body to clamp the terminal assembly 22 against the mounting face 37 in the body 16. This rivet constitutes the sole mounting of the terminal assembly 22.

The terminal assembly 23 is provided with a fixed contact 38 at one end and a connecting portion 39, which connects to the lead wire 28, at its other end. The structures of the lead wire connecting portions may be similar in the two terminal assemblies as illustrated. Here again a single rivet 41 projects through an opening 42 in the body 16 and the central portion of the terminal assembly 23 to hold the terminal assembly in position against a mounting surface 43 formed in the body 16. Exact positioning and support of the fixed contact 38 is insured by providing a small projection 44 in the body 16 which engages the underside of the terminal assembly adjacent to the fixed contact 38.

The switch is operated by bimetallic snap disc 46 which snaps between its two positions of stability when predetermined temperatures are reached. The snap disc 46 is radially located by a shoulder 47 in the body 16 and is axially located adjacent to a radial face 48 by the disc retainer 18. The disc retainer 18 is recessed at 49 to provide clearance for the disc when the disc is in the downward position of stability as illustrated in FIG. 4.

Extending between the disc 46 and the mobile contact support member 28 is an insulating bumper 51 guided in a passage 52 in the body 16. When the disc 46 is in the position illustrated, the switch closes and when the disc snaps through to its upper position of stability, the bumper 51 is caused to move up against the support arm 28 to cause the switch to open.

The disc retainer 18 is secured in position on the main body member 17 by four tabs 53 (best illustrated in FIGS. 3 and which are bent over mating shoulders 54 in the body member 16. These tabs securely connect the disc retainer to the main body member 16 and the tabs 19 separately secure the cover member 17 to the main body member 16. The disc retainer is also proportioned to extend past the lower side of the rivets 34 and 41 while being spaced therefrom so that the lower ends of the electrically charged rivets are protected against access and shorting.

The body member 16 is preferably formed with an upstanding fiange 56 which extends up into and mates with a downwardly extending flange 57 on the cover member 17 to provide lateral positioning of the two body members and to provide a path of substantial length between the electrically charged switch element and the exterior of the body. The lower edge of the flange 57 seats against a surface 58 on the member 16 to cooperate with the tabs 53 in vertical positioning of the two members. The ends of the body member 16 are formed with grooves 59 which cooperate with grooves 61 formed in the cover member 17 to closely fit and encircle the insulation of the lead wires 27 and 28. With this structure the body assembly supports the lead wires beyond the terminal connections and there is substantially no tendency for the lead wire to break at the terminal, a place where failures often occur when support is not provided. Similarly the cover member 17 is preferably formed with depending walls 62 and 63 adjacent to the terminal assemblies 22 and 23 respectively. These walls act to provide a dust barrier to resist dirt entry into the switch chamber. They also provide stiffening of the cover member 17 and some support for the terminals.

The body assembly in cooperation with the disc retainer provides complete enclosure for the functioning elements of the thermostat so dirt cannot enter the thermostat to cause malfunction. Also the structure is arranged so that no external portions are electrically charged. Further the structure is arranged so that the terminals are aligned with and in substantially the same plane as the switch elements. With this structure tension loads applied to the lead wires do not cause any lateral deformation of the contact supporting members. Consequently the lead wires can be subjected to high tension loads without causing any material change in the calibration of the thermostat. Also with this structure it is possible to make the thermostat so that its width is substantially equal to the diameter of the disc and its thickness is less than its width. Consequently it can be quite small so that it can be used in confined locations.

During assembly of the thermostat, the terminal assemblies are connected to the associated leads and are then riveted in place by the associated rivets 34 and 41. The two ends of each of the rivets are accessible because the cover member 17 and the disc retainer 18 are not then in place. The bumper 51 is then placed in the opening 52 and the disc is then placed in position. The disc retainer 18 is then mounted in position by bending the tabs 53 over the associated surfaces 54. This completes the assembly of the functioning portions of the thermostat. In many cases where functional testing is required, the thermostat is then cycled to insure that it operates correctly within the temperature range desired. Since several thermostats are normally connected in series during the manufacture, this ability to cycle the thermostat before the cover is positioned in place is desired since it permits electrical connection, for testing, to the exposed upper surfaces of the terminals and rivets. If the thermostat functions correctly the cover member 17 is then properly positioned and the tabs 19 are bent into place to complete the assem bly of the thermostat.

Because only two fasteners are required to secure the switch and terminals elements in position, the assembly cost is low. Similarly the use of disc retainer to perform the several functions of mounting the disc in position, covering the exposed rivet ends, and securing the cover in place, futher reduces manufacturing costs. The use of a prewired terminal and contact assembly also permits the internal positioning of the terminal connection and the supporting of the lead wires to prevent breakage thereof.

Although a preferred embodiment of this invention is illustrated, it is to be understood that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention disclosed.

I claim:

1. A thermostat comprising an elongated body member formed with a lengthwise switch chamber open along one face thereof, first and second terminal units extending lengthwise of said chamber, a single rivet securing each terminal unit in said switch chamber, said terminal units providing cooperating switch contacts one of which is movable between a switch opened and a switch closed position, a bimetallic snap disc, a disc retainer secured to said body locating said disc with respect to said body, a bumper operably connected between said movable switch contact and disc operable to move said movable switch contact between said opened and closed positions in response to movement of said disc, a lead wire connected to each of said terminal units extending out of the adjacent end of said body, a cover member positioned over said one face of said switch chamber and cooperating with said body member to enclose said terminal units, the end of said body member and cover member providing surfaces cooperating to closely fit and support said leads at a location spaced from said terminal units.

2. A thermostat as set forth in claim 1 wherein said disc retainer operates to secure said cover member to said body member.

3. A thermostat as set forth in claim 2 wherein said disc retainer is provided with separate fastening means to secure said disc retainer to said body member and to separately secure said cover member to said body member.

4. A thermostat as set forth ih claim 3 wherein said disc retainer is sheet metal and said fastening means are separate projections deformed into engagement with-mating surfaces of said body member and cover member.

5. A thermostat as set forth in claim 4 wherein said body is formed with access openings open to one end of said rivets, and said disc retainer extends over and closes said openings, said rivets being spaced from said retainer, said body member and said cover member cooperating with said disc retainer to totally enclose all of the parts of the thermostat which carry electricity.

6. A thermostat as set forth in claim 4 wherein said body member and cover member cooperate to form an elongated rectangular body assembly, said lead wires projecting from opposite ends of said assembly, and said disc is located adjacent one lateral face of said body assembly.

7. A thermostat as set forth in claim 6 wherein said body assembly has a width in the direction of said lateral face which is substantially equal to the diameter of said disc, and the thickness of said body assembly normal to said one lateral face is less than said width.

8. A thermostat as set forth in claim 1 wherein said body is formed with access openings open to one end of said rivets, and said disc retainer extends over and closes said openings, said rivets being spaced from said disc retainer, said body member and said cover member cooperating with said disc retainer to totally enclose all of the parts of said thermostat which carry electricity.

9. A thermostat comprising a body, first and second terminal contact units mounted in said body each providing a contact support portion at one end and a wire connector portion at the other end, a fixed contact mounted on said contact support portion of said first terminal unit, a mobile contact mounted on the contact support portion of said second terminal unit, a lead wire connected to each wire connector portion, thermal responsive means operably connected to said mobile contact operable to move said mobile contact into and out of engagement with said fixed contact, and a cover cooperating with said body to enclose the connection between said lead wires and said terminal connectors, said cover and said body having cooperating surfaces which closely fit and support said lead wires at a location spaced from said terminal connectors, said cover and body also cooperating to totally enclose said switch and prevent entry of foreign material into the area of said switch.

10. A thermostat as set forth in claim 9 wherein said body and cover cooperate to closely fit and enclose said lead wires to support said lead Wires at a location spaced from said terminal units.

11. A thermostat as set forth in claim 9 wherein said thermal responsive means includes a bimetallic snap disc mounted in said body, and disc retainer cooperating to position said disc in said body and secure said cover to said body.

12. A thermostat as set forth in claim 11 wherein said terminal units and lead wires are substantially aligned and in the same plane.

References Cited UNITED STATES PATENTS 3,221,115 11/1965 Feher. 3,219,783 11/1965 Odson 337--354 XR 2,760,173 8/1956 Cunningham. 2,035,035 3/1936 Weeks 337-112 XR BERNARD A. GILHEANY, Primary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R. 

